cdc.gov/coronavirus

Early safety monitoring for additional 

COVID-19 vaccine doses: 

Reports to VAERS and v-safe

Advisory Committee on Immunization Practices

September 22, 2021

Anne M. Hause, PhD MSPH

V-safe Team Co-Lead

COVID-19 Vaccine Task Force
CDC vaccine safety monitoring

v-safe VAERS VSD CISA Project

Full list of U.S. COVID-19 vaccine safety monitoring systems

https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety.html

• COVID-19 vaccines are being administered under the most intensive vaccine 

safety monitoring effort in U.S. history

• Strong, complementary systems are in place―both new and established 

2
CDC vaccine safety monitoring

v-safe VAERS VSD CISA Project

Full list of U.S. COVID-19 vaccine safety monitoring systems

https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety.html

• Authorized COVID-19 vaccines are being administered under the most 

intensive vaccine safety monitoring effort in U.S. history

• Strong, complementary systems are in place―both new and established 

3
+ co-managed by

CDC and FDA

Vaccine Adverse Event 

Reporting System

http://vaers.hhs.gov

VAERS is the nation’s early warning system for vaccine safety

4
VAERS accepts reports from everyone

Key strengths

 Rapidly detects potential 

safety problems 

 Can detect rare adverse 

events

Key limitations

 Inconsistent quality and 

completeness of information

 Reporting biases

 Generally, cannot determine 

cause and effect

Regardless of the plausibility of the vaccine causing the event or the 

clinical seriousness of the event

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Reports to VAERS following dose 3 of mRNA COVID-19 

vaccination, by age group and sex

Age group, years n (%)

12–17 48 (2)

18–49 622 (24)

50–64 654 (26)

≥65 1,239 (48)

Total 2,563

 Median age 64 years (range: 12–100)

 Most reports (61%) among women

Sex n (%)

Male 979 (38)

Female 1,570 (61)

Unknown 14 (1)

Total 2,563 

Includes data collected during December 14, 2020–September 17, 2021

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Reports to VAERS following dose 3 of 

mRNA COVID-19 vaccination, by race 

and ethnicity

Race or ethnicity Reports (%)

Hispanic 143 (6)

Non-Hispanic

AI/AN 11 (<1)

Asian 51 (2)

Black 89 (3)

NHPI 1 (<1)

White 998 (39)

Multiracial 14 (1)

Other 8 (<1)

Unknown/not reported 1,248 (49)

Total 2,563 

 Most reports either

• Unknown/not reported race or ethnicity (49%)

• White, non-Hispanic race and ethnicity (39%)

Includes data collected during December 14, 2020–September 17, 2021 for persons 12+ years of age. Hispanic also includes persons identified of Hispanic ethnicity of unknown race.

Abbreviations: AI/AN = American Indian/Alaska Native; NHPI = Native Hawaiian or other Pacific Islander. 7
Reports to VAERS following dose 3 of mRNA COVID-19 

vaccination

Manufacturer Non-serious Serious Total

Pfizer-BioNTech 1,175 (95%) 68 (5%) 1,243

Moderna 1,257 (95%) 63 (5%) 1,320

Total 2,432 (95%) 131 (5%) 2,563

 Regardless of manufacturer, 95% of reports non-serious

Includes data collected during December 14, 2020–September 17, 2021 for persons 12+ years of age. 

Per federal law, includes reports of hospitalization, prolongation of existing hospitalization, life threatening condition, permanent disability, congenital deformity or birth defect, or death 8
Most frequently reported adverse events to VAERS following dose 3 

of mRNA COVID-19 vaccination, by seriousness

Includes data collected during December 14, 2020–September 17, 2021 for persons 12+ years of age. Per federal law, includes reports of hospitalization, prolongation of existing hospitalization, life 

threatening condition, permanent disability, congenital deformity or birth defect, or death.

* Not mutually exclusive

Serious (n = 131) Non-serious (n= 2,432)

Rank Adverse event* n (%)

1 Extra dose administered 40 (31)

2 Fever 27 (21)

3 Dyspnea 23 (18)

4 Death 18 (14)

5 Fatigue 14 (11)

Rank Adverse event* n (%)

1 Extra dose administered 945 (39)

2 Fever 323 (13)

3 Headache 274 (11)

4 Fatigue 269 (11)

5 No adverse event 243 (10)

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Reports of death to VAERS following dose 3 of mRNA 

COVID-19 vaccination

 Median age = 76 years (range: 47–93)

 Median time from 3rd dose to death = 

1 day (range: day of vaccination – 12)

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Preliminary impression of 

cause of death* Reports

Respiratory and/or cardiac arrest 7

Unable to assess 4

Pulmonary embolism 2

Sepsis 1

Accident/trauma 1

Cancer 1

COVID-19 pneumonia 1

Total 18

Includes data collected during December 14, 2020–September 17, 2021 

* Based upon physician review of initial report and available documentation, including death certificates
Smartphone-based active safety monitoring

http://cdc.gov/vsafe

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Active safety monitoring for COVID-19 vaccines

v-safe is a CDC smart-phone based monitoring program for COVID-19 

vaccine safety

• Uses text messaging and web surveys to check in with vaccine recipients after 

vaccination

• Can register at any time: after 1st, 2nd, or 3rd dose

• Solicits participants' reports on how they feel after COVID-19 vaccination

• Local injection site reactions

• Systemic reaction

• Health impacts (unable to perform normal daily activities, missed school 

or work, or received care) 

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Demographic summary of 21,935 v-safe participants who 

reported an additional dose

Includes participants who completed at least one survey in the first week after additional dose, data collected during August 12–September 19, 2021

Abbreviations: AI/AN = American Indian/Alaska Native; NHPI = Native Hawaiian or other Pacific Islander.

Characteristic % of participants

Sex

Female 63.4

Male 35.7

Unknown 1.0

Age group (years)

0-17 0.3

18-49 29.2

50-64 29.8

65-74 30.5

75-84 9.5

≥85 0.8

Characteristic % of participants

Ethnicity

Hispanic/Latino 8.2

Not Hispanic/ Latino 87.7

Unknown 4.2

Race

AI/AN 0.4

Asian 5.2

Black 5.6

NHPI 0.3

White 82.4

Multiracial 1.9

Other 2.0

Unknown 2.2

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Patterns of vaccination for 21,935 v-safe participants who 

reported an additional dose

Moderna (%) Pfizer-BioNTech (%) Janssen (%)* Total

Moderna 10,331 (98.6) 196 63 6,903

Pfizer-BioNTech 142 11,082 (98.2) 64 11,288

Janssen 4 6 47 (27.0) 57

Total 10,477 11,284 174 21,935

Primary series

Additional

dose

Includes participants who completed at least one survey in the first week after additional dose, data collected during August 12–September 19, 2021

* Includes persons who received Janssen as their primary series and one additional dose of vaccine from the listed manufacturers 14
Most common solicited reactions reported at least once 0-7 

days after dose 3 of Moderna or Pfizer-BioNTech vaccine

Includes 21,413 participants who completed at least one survey in the first week after additional dose, data collected during August 12–September 19, 2021

0

10

20

30

40

50

60

70

80

90

100

Pain - injection

site

Fatigue Myalgia Headache Fever Swelling -

injection site

Joint pain Chills Redness Nausea

Percentage

Moderna Pfizer-BioNTech

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Comparison of reactions and health impact events reported at least once 

in days 0-7 after Pfizer-BioNTech vaccination, by dose

Includes 6,267 participants who completed at least one survey in the first week after each dose, data collected during August 12–September 19, 2021 

* Odds of reporting an event following dose 2 and 3 compared using multivariable generalized estimating equations model that accounted for the correlation 

between registrants and adjusted for demographic variables; p-values less than 0.05 were considered statistically significant

1.1 1.5 1.4

0

10

20

30

40

50

60

70

80

90

100

Any injection site reaction Any systemic reaction Any health impact Unable to perform daily

activities

Unable to work Needed medical care

Percentage

Dose 1 Dose 2 Dose 3

*

* *

* *

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Comparison of reactions and health impact events reported at least once 

in days 0-7 after Moderna vaccination, by dose

Includes 6,242 participants who completed at least one survey in the first week after each dose, data collected during August 12–September 19, 2021 

* Odds of reporting an event following dose 2 and 3 compared using multivariable generalized estimating equations model that accounted for the correlation 

between registrants and adjusted for demographic variables; p-values less than 0.05 were considered statistically significant

0.8 1.5 1.9

0

10

20

30

40

50

60

70

80

90

100

Any injection site reaction Any systemic reaction Any health impact Unable to perform daily

activities

Unable to work Needed medical care

Percentage

Dose 1 Dose 2 Dose 3

* *

*

* *

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Limitations of early safety monitoring for an additional 

COVID-19 vaccine dose

 V-safe population likely not representative of the vaccinated U.S. population

 Additional dose recipients likely included immunocompromised and non- immunocompromised persons

• V-safe does not include information about immune status

• Immunocompromised persons might have different reactogenicity than 

immunocompetent persons

 Data available now are insufficient

• To determine patterns of adverse events after receipt of an additional dose 

from a manufacturer different from the primary series

• To identify rare adverse events

 Complete medical review of deaths following vaccination reported to VAERS is 

dependent on availability of medical records, death certificates, and autopsy 

reports, which may be delayed or not available

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Summary

 No unexpected patterns of adverse events were identified

 95% of VAERS reports following dose 3 of COVID-19 vaccination were nonserious

 Over 21,000 v-safe registrants reported an additional dose

• Most reported a primary mRNA vaccine series followed by dose 3 from 

the same manufacturer

• Local and systemic reactions were reported slightly less frequently 

following dose 3 than dose 2

• Similar to Pfizer-BioNTech phase 3 clinical trial (included 306 persons)1

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1 https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-initiate-rolling-submission 
Next steps

 VAERS and v-safe will continue to monitor safety of additional doses of 

COVID-19 vaccination

 The Vaccine Safety Datalink (VSD) will incorporate additional doses of 

COVID-19 vaccination into weekly near real-time sequential monitoring

 The Clinical Immunization Safety Assessment (CISA) Project will continue to 

be available to consult on clinically complex adverse events following 

additional dose of COVID-19 vaccination

 CDC will update ACIP as additional data become available

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For more information, contact CDC

1-800-CDC-INFO (232-4636)

TTY: 1-888-232-6348 www.cdc.gov

The findings and conclusions in this report are those of the authors and do not necessarily represent the 

official position of the Centers for Disease Control and Prevention.

Thank you!